http://earlyamerica.com/review/summer97/secular.html(chock full of good info and specific quotes from the founding fathers expressing that nation is secular not religious)
Little-Known U.S. Document Signed by President Adams Proclaims America's Government Is Secular
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Although, indeed, many of America's colonial statesmen practiced Christianity, our most influential Founding Fathers broke away from traditional religious thinking. The ideas of the Great Enlightenment that began in Europe had begun to sever the chains of monarchical theocracy. These heretical European ideas spread throughout early America. Instead of relying on faith, people began to use reason and science as their guide. The humanistic philosophical writers of the Enlightenment, such as Locke, Rousseau, and Voltaire, had greatly influenced our Founding Fathers and Isaac Newton's mechanical and mathematical foundations served as a grounding post for their scientific reasoning.
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Treaty of Tripoli
Unlike governments of the past, the American Fathers set up a government divorced from religion. The establishment of a secular government did not require a reflection to themselves about its origin; they knew this as an unspoken given. However, as the U.S. delved into international affairs, few foreign nations knew about the intentions of America. For this reason, an insight from at a little known but legal document written in the late 1700s explicitly reveals the secular nature of the United States to a foreign nation. Officially called the "Treaty of peace and friendship between the United States of America and the Bey and Subjects of Tripoli, of Barbary," most refer to it as simply the Treaty of Tripoli. In Article 11, it states:
"As the Government of the United States of America is not in any sense founded on the Christian religion; as it has in itself no character of enmity against the laws, religion, or tranquillity, of Musselmen; and as the said States never have entered into any war or act of hostility against any Mehomitan nation, it is declared by the parties that no pretext arising from religious opinions shall ever produce an interruption of the harmony existing between the two countries."
The preliminary treaty began with a signing on 4 November, 1796 (the end of George Washington's last term as president). Joel Barlow, the American diplomat served as counsel to Algiers and held responsibility for the treaty negotiations. Barlow had once served under Washington as a chaplain in the revolutionary army. He became good friends with Paine, Jefferson, and read Enlightenment literature. Later he abandoned Christian orthodoxy for rationalism and became an advocate of secular government. Barlow, along with his associate, Captain Richard O'Brien, et al, translated and modified the Arabic version of the treaty into English. From this came the added Amendment 11. Barlow forwarded the treaty to U.S. legislators for approval in 1797. Timothy Pickering, the secretary of state, endorsed it and John Adams concurred (now during his presidency), sending the document on to the Senate. The Senate approved the treaty on June 7, 1797, and officially ratified by the Senate with John Adams signature on 10 June, 1797. All during this multi-review process, the wording of Article 11 never raised the slightest concern. The treaty even became public through its publication in The Philadelphia Gazette on 17 June 1797.
So here we have a clear admission by the United States that our government did not found itself upon Christianity. Unlike the Declaration of Independence, this treaty represented U.S. law as all treaties do according to the Constitution (see Article VI, Sect. 2).
Although the Christian exclusionary wording in the Treaty of Tripoli only lasted for eight years and no longer has legal status, it clearly represented the feelings of our Founding Fathers at the beginning of the U.S. government.